In Dense Wavelength Division Multiplexing (DWDM) systems, light at multiple wavelengths is modulated with streams of digital information, and then the modulated light beams at different wavelengths, termed “wavelength channels”, are combined for joint propagation in an optical fiber.
To identify wavelength channels in a DWDM system, a pilot tone may be applied to communication channels within the optical telecommunications system. The pilot tone is typically a low frequency modulation of a channel's optical power level. The pilot tone may be used for channel optical performance monitoring, and may also carry information associated with the channel, such as, but not limited to, its wavelength, baud rate, modulation format and other identification information for supervisory, control, equalization, continuity, synchronization, or reference purposes.
By providing this pilot tone, channel power can be monitored by a low cost, low speed pilot-tone detector.
In many current systems, the pilot tone is subject to degradation caused by the interaction and superposition of optical signals in the transmission fiber.
Therefore, there is a need for an improved system and method for pilot tone based optical performance monitoring.